Watch the end of an era as the last flight of a Delta II takes off

Tomorrow morning, a rocket of nearly 30 years will make its last trip in space. The Delta II, a vehicle manufactured by United Launch Alliance and launched for the first time in 1989, will fly one last time, sending an Earth observation satellite into orbit for NASA. If tomorrow 's mission goes well, it will serve as the Delta II' s successful 100th flight in a row, while ending a rocket that launched mobile gear on Mars and spacecraft to the airbelt. asteroids.

On this latest flight is NASA's ICESat-2 satellite, which measures how land ice and sea ice around the Earth's poles evolve over time. This is a follow-up mission of the original spacecraft ICESat, which observed the Earth's transformation from 2003 to 2009. Both satellites use the same sophisticated tool: a pulsed laser that bounces off the surface of the planet. the ice as well as the thickness of the ice cap.

"ICESat-2 is really building on the lessons learned from the first ICESat," says Tom Neumann, assistant researcher on the ICESat-2 project at NASA's Goddard Space Flight Center. The edge. "And we changed the design between the two. It will be a much more powerful instrument and a much richer dataset. "

Image: NASA

ICESat-2 is an appropriate mission for the latest Delta II rocket, which has sent many spacecraft into orbit around the Earth. Derived from the ancient ballistic missile technology, the Delta II was responsible for setting up the Spitzer Space Telescope on top of our planet, as well as various weather observatories and meteorological satellites. But the vehicle has also made important space missions. The Delta II was NASA's Kepler spacecraft route and sent NASA's Spirit and Opportunity rovers to the Martian surface. And aside from two failures in the 1990s, the Delta II proved to be a pretty reliable rocket for the United Launch Alliance.

But despite its reliability and long history, the ULA is ready to remove the vehicle. It does not fly very often and the ULA focuses on consolidating its fleet to the existing Atlas V and Delta IV Heavy launchers while developing a new rocket called Vulcan. All three can offer the same capabilities as the Delta II, without the added cost of Delta II operation.

The last flight of the rocket is scheduled to take off from Vandenberg Air Force Base in California at 8:46 am Saturday. ICESat-2 will be deployed in orbit approximately 52 minutes after take-off. The mission team will then perform some system checks on the spacecraft, with the intention of turning on the satellite laser, ATLAS, approximately two weeks after launch. Once ATLAS is considered healthy, the plan is to start collecting data by mid-October to the end of the month.

ICESat-2 is expected to last at least three years in orbit, with enough fuel to last up to seven years if necessary. Meanwhile, the satellite will bombard the Earth with lasers. The ICESat-2 generates a laser light that is divided into six beams, each sending 10,000 pulses to the ground per second. These lasers hit the ice of our planet and are reflected to the onboard telescope of the spacecraft. ICESat-2 then measures the time needed for the lasers to return to the satellite, which indicates the height of the vehicle above the Earth. This finally indicates to scientists the thickness of the ice caps under the satellite.

Image: NASA

The ICESat-2 orbit will take the vehicle to the same location on Earth every 91 days, allowing the mission team to measure the evolution of the polar ice every few months. And since it is in space, ICESat-2 can observe ice all year round, unlike other ice mapping campaigns on Earth. NASA's IceBridge operation is an aeronautical mission that studies Arctic and Antarctic ice caps, but can not fly when weather conditions become too inhospitable. In addition, poles are large areas to cover. "The ice caps are really big," says Neumann. "Antarctica, for example, is about the size of the mainland of the United States and Mexico, and it is simply not possible to cover such an area by plane. If you want an image of the evolution of the ice sheet, you really have to look at it from the point of view of space.

This is good news for those who wish to learn how the changing sea will impact our oceans and our atmosphere. As the ice in Greenland and Antarctica decreases, all this lost water is discharged into the oceans, contributing to sea level rise. Moreover, the thickness of the ice also influences the atmosphere of the Earth. which affects the exchange of heat and moisture between the polar oceans and the air. "So, by measuring thickness with ICESAT-2, we will have better information to predict how sea ice will change," says Neumann.

NASA's coverage of the launch of ICESat-2 is expected to start at 8:10 am. Check that the last Delta II sends an indispensable laser in orbit.